Optical disk devices that play (or regenerate) information recorded on a CD, CD-ROM, DVD, DVD-ROM, etc., and optical disk devices that record/play information with respect to a CD-R, CD-RW, DVD-R, DVD-RW, etc. are known. These optical disk devices are constructed so as to record and/or play information by shining a light spot from an optical pickup onto the information recording surface of a mounted optical disk and detecting the reflected light. The relative position of the optical disk and optical pickup in such an optical disk device must be precisely adjusted, because the light spot must accurately shine onto the track on which the information on the optical disk is recorded.
Thus the optical disk device has a tracking adjustment system that performs tracking adjustment with respect to the mounted optical disk, a focus adjustment system that adjusts the focal point depth of the light spot with respect to the optical disk, and a sled adjustment system that adjusts the sled position of the optical pickup. These adjustment systems are driven and controlled by a control means based on an error signal detected by the optical pickup.
In such an optical disk device, in order to cause a track jump operation to be performed to move to the target track by jumping across multiple tracks all at once, first, by means of the tracking adjustment system, one adjusts the attitude of the object lens that constitutes the optical pickup while detecting the tracking error signal output from the optical pickup, and moves the center of the light spot to the target track. Next, in correspondence with this, a so-called traverse movement is executed by means of the sled adjustment system to bring the optical pickup to immediately below the target track.
Heretofore, such control of the tracking adjustment system and sled adjustment system was performed using an autosequencer inside a control digital signal processor (DSP) based on the tracking error signal output from the optical pickup. And this control was performed in such a way that the speed of the traverse is kept constant by making the tracking adjustment system and the sled adjustment system move in cooperation.
But there have been problems such as the following in conventional optical disk devices in which control is thus done so that the tracking adjustment system and sled adjustment system move in cooperation based on the tracking error signal. That is, there has been the problem that even if it is a tracking error signal that is caused by a disturbance such as eccentricity of the optical disk and a treatable tracking error signal occurs by position adjustment of the tracking adjustment system alone, operation control of the sled adjustment system may take place in response, and the sled adjustment system may react oversensitively.
In this case one could conceive of a method whereby, by passing the tracking signal through a low-pass filter, one causes the sled adjustment system not to operate for a tracking error signal that is below a prescribed threshold value, but if the sensitivity is set too high, one cannot prevent the sled adjustment system from reacting oversensitively, and if the sensitivity is set too low, it will be lacking in responsiveness during sled position adjustment. Therefore this method will not provide an adequate solution.